Epidemiology and Population Health, Stanford University, Stanford, California, USA kcobb@stanford.edu. Menzies Health Institute Queensland, Griffith University, Nathan, Queensland, Australia. Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA. Deptartment of Health & Medical Sciences, Swinburne University of Technology, Hawthorn, Victoria, Australia. Optimum Performance Analytics Associates LLC, Apex, North Carolina, USA. Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York, USA. Departments of Biomedical Engineering and Statistics, Northwestern University, Evanston, Illinois, USA. Exercise & Sport Science, Faculty of Health Sciences, University of Sydney, Sydney, New South Wales, Australia. Australian Institute of Sport, Canberra, Australian Capital Territory, Australia. Department of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales, Australia. Health, Kinesiology, and Recreation; Department of Physical Therapy and Athletic Training, University of Utah Health, Salt Lake City, Utah, USA. School of Public Health, University of Adelaide, Adelaide, South Australia, Australia. Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland.